Implement /experimental/blueprints/UUID/composes endpoint which return list of composes associated with the blueprint. See the sketch:

https://www.sketch.com/s/669c80df-098c-4296-b689-b4e0702d8261/a/dgdQoxj

The result payload needs to be compatible with the current composes endpoint which will be used when no blueprint is selected:

https://www.sketch.com/s/669c80df-098c-4296-b689-b4e0702d8261/a/j4eWKxb